Thermometer guns used to screen for coronavirus are 'notoriously' unreliable experts say, warning against improper use and false temperatures

Morgan McFall-Johnsen

02/15/2020

Tell your friends

A new coronavirus spreading across the globe has led to temperature screenings at airports, Chinese cities, and businesses.

China coronavirus temperature check

Thomas Peter/Reuters

The thermometer guns used in these screenings are "notoriously not accurate and reliable," since many screeners hold them at the wrong distance or use them in the wrong environments, experts told The New York Times.

Demand for thermometer guns has spiked since the coronavirus outbreak began, leaving some manufacturers struggling to keep up.

As officials struggle to contain a new coronavirus spreading across the globe, travelers worldwide are undergoing unreliable temperature screenings, experts say.

The new coronavirus, first discovered in Wuhan, China in December, has infected nearly 67,000 people and killed more than 1,500, mostly within China. (For the latest case total and death toll, see Business Insider's live updates .)

Airports, Chinese cities, and even Apple stores have instituted temperature checks to identify potential patients and prevent the virus's spread. To do this, many governments and businesses rely on thermometer guns devices that use infrared sensors to measure a person's surface temperature without touching their skin.

"These devices are notoriously not accurate and reliable," Dr. James Lawler, a medical expert at the University of Nebraska's Global Center for Health Security, told The New York Times . "Some of it is quite frankly for show."

That means that many coronavirus cases go undetected through these temperature screenings.

Why thermometer guns are often unreliable

Most people wielding thermometer guns hold them too far from or too close to the subject, yielding temperature measurements that are either too hot or too cold, according to experts who spoke with The New York Times.

coronavirus thermometer gun infrared temperature

Vincent Thian/AP Photo; Hannah McKay/Reuters

Lawler said that thermometer guns had suggested he was dying of hypothermia as he traveled through West Africa during the 2014-2016 Ebola outbreak.

"My temperature was often 35 degrees Celsius or lower, which starts to become incompatible with life," Lawler said. "So I'm not sure those were accurate."

According to industrial supply company Grainger , the correct distance to hold a handheld infrared thermometer depends on the size of the target.

What's more, environments like a dusty road or a hot car can affect the infrared temperature measurement.

Even if used correctly, thermometers won't catch everyone who could spread the new virus. Studies show that infected people can go up to 14 days without showing symptoms, and some preliminary research suggests that period could last as long as 24 days. It's still unclear if infected people without symptoms can spread the virus to others.

Some patients have experienced nausea, vomiting, or diarrhea before they develop a fever . They could still be infectious at that stage. If someone has taken a fever-suppressing medication, they could show normal temperatures.

The World Health Organization (WHO) acknowledges that some infected people will pass temperature screenings, but still maintains that the checks reduce the "risk of importation of the disease." According to the WHO, most of the cases that traveled outside China were detected through screening as they entered another country.

On the flip side, a high temperature does not necessarily indicate illness. Temperature screenings can flag people who aren't infected.

"They could have been exercising, they could be taking certain drugs," Jim Seffrin, an infrared devices expert at the Infraspection Institute in New Jersey, told The New York Times. "A person who's been trying to catch a flight in an airport for which they are late they may have run down a concourse."

"It's the most overwhelming thing I've had to deal with in my life," Gary Strahan, the CEO of infrared thermometer technology company Infrared Cameras, told The New York Times. "We've got people coming to us directly, saying: 'Can you supply 1,000 cameras? Can you supply 2,000 cameras?'"

Strahan added that he had been working 4 a.m. to 10 p.m. daily to keep up with new orders. Mo Yingchun, a general manager at thermometer gun manufacturer Alicn Medical in Shenzhen, China, said that prices have spiked to three or four times their usual level. Mo said that China's quarantine efforts have cut off many of the manufacturer's employees, preventing factories from operating at full capacity.

"Even the governments are fighting for the products among themselves," Mo said. "Local governments want to guarantee their own needs first."

Even he agreed that the infrared thermometers are not always reliable. Mo added that his company's devices are typically used to check infants' temperatures indoors.

"The thermometer guns are used only for quick screening and are not as accurate as traditional thermometers," Mo said. "It was a small industry, and if it weren't for the outbreak, it will not be put in the spotlight."